function [scnls starttimes endtimes] = query_file(ds, filename)
   % QUERY_FILE retrieves scnl, starttime and endtime information for all
   % objects of intrest with a file
   % [scnls starttimes endtimes] = query_file(datasource, filename);
   
   if ~requires_file(ds)
      warning('irrelevent request, no filenames associated with this datasource');
      scnls = scnlobject;
      return
   end
   if isa(filename,'cell')
      filename = filename{1};
   end;
   if ~exist(filename,'file')
      warning('file does not exist');
      scnls =  scnlobject;
      return
   end
   
   obj = ds.interpreter(filename);
   scnls = get(obj,'scnlobject');
   starttimes = get(obj,'start');
   endtimes = get(obj,'end');
   
   %interpret file
   %keep scnls only
   
end